Barataria Basin Research Articles

Living on the Edge: Multi-Scale Analyses of Bird Habitat Use in Coastal Marshes of Barataria Basin, Louisiana, USA

Coastal marsh loss, combined with expected sea-level rise, will cause inundation and extensive shifts to vegetation and salinity regimes that may affect bird species dependent on coastal ecosystems worldwide. Within coastal-marsh habitats, birds provide key targets for coastal management goals. However, limited information on bird-habitat relationships within coastal marshes inhibits the development of restoration projects targeted to bird species. We surveyed birds bi-monthly within Barataria Basin, LA from July 2014 to December 2015 to compare their use between fresh and saline coastal marshes. Additionally, we examined habitat use at finer spatial scales to assess preference for marsh-edge microhabitats. Edge habitat supported 1.8 times more bird species (guild) richness than emergent and open-water habitat. We concluded that future modelling efforts would be improved if models incorporate edge effects for birds in coastal marshes that extend 20 m from emergent vegetation into open water, with a reduced effect if marsh types convert from fresh to saline. Our data will be useful to simulate the effects of changes in marsh type, area, and edge on habitat quality for birds in coastal Louisiana and will inform habitat restoration and management decisions aimed at optimizing bird use.

Applications and utility of the surface elevation table–marker horizon method for measuring wetland elevation and shallow soil subsidence-expansion

Byrnes et al. (Geo-Marine Letters 39:265–278, Byrnes et al. 2019) present subsidence data for Barataria Basin located south and west of New Orleans in coastal Louisiana to better inform wetland protection and restoration planning by the Louisiana Coastal Protection and Restoration Authority. They measured subsidence using geodetic GPS elevation surveys of rod benchmarks, similar to the rod benchmarks of the surface elevation table–marker horizon (SET-MH) method used to measure surface biophysical processes influencing elevation dynamics and shallow subsidence (i.e., subsidence occurring above the base of the rod) in coastal wetlands. Byrnes et al. (Geo-Marine Letters 39:265–278, Byrnes et al. 2019) argue that (1) SET-MH measures should not be included in subsidence measures because subsidence is a purely geologic process, separate from biophysical processes occurring in the active marsh zone, (2) shallow subsidence measured by the SET-MH method in deep Holocene sediments are not valid because of downdrag on the rod, and (3) high spatial variability of wetland surface processes precludes the ability to make meaningful estimates of subsidence using the SET-MH method. This reply paper presents an extensive summary of the peer-reviewed literature that refutes all three of these claims and demonstrates that it is not only reasonable but also essential to apply the SET-MH method to obtain a complete as possible assessment of surface elevation dynamics to inform coastal wetland restoration and management planning in Barataria Basin and other coastal wetlands worldwide.

English

Abstract Anthropogenic modifications to river-floodplain systems can decouple floodplains from mainstem inputs, alter flood pulse dynamics, and disrupt population dynamics and trophic web stability of aquatic biota. The Atchafalaya River Basin (ARB) receives an annual flood pulse from the Mississippi River that contributes to high crayfish abundance. Conversely, reduced crayfish abundance in the Barataria Basin (BB) is attributed to the system no longer receiving an annual flood pulse from the Mississippi River. Therefore, the purpose of this research was to determine if the absence of an annual flood pulse and reduced crayfish abundance influenced the diets of carnivorous fishes by examining stomach contents of fishes from both basins. Stomach contents were grouped as crayfish, fish, non-crayfish invertebrate, and herpetological. Although the percent occurrence of crayfish in fish stomachs differed between floodplain inundation and low-water periods in the ARB, crayfish were still the major diet constituent of ARB fishes during both periods. Non-crayfish invertebrate was the major diet constituent in BB fishes, with crayfish ranking as the second fewest diet constituent present. Our results demonstrate how flood pulse dynamics influence crayfish, and ultimately trophic webs, in large river-floodplain systems.

Restoring barrier habitat in Louisiana to compensate for natural resource injuries: Shell Island and Chenier Ronquille Barrier Restoration Projects

Coastal Louisiana received significant funds tied to BP penalties as a result of the Deepwater Horizon incident. As it is widely considered that the State of Louisiana sustained most of the damage due to this incident, there has been a firm push to waste no time in implementing habitat restoration projects. Sustaining the land on the coast of Louisiana is vital to our nation’s economy, as several of the nation’s largest ports are located on the Gulf coast in Louisiana. In addition, the ecosystems making up the Louisiana coast are important to sustain some of the largest and most valuable fisheries in the nation. Funded by BP Phase 3 Early Restoration, the goals of the Natural Resource Damage Assessment (NRDA) Outer Coast Restoration Project are to restore beach, dune, and marsh habitats to help compensate spill-related injuries to habitats and species, specifically brown pelicans, terns, skimmers, and gulls. Four island components in Louisiana were funded under this project; Shell Island Barrier Restoration, Chenier Ronquille Barrier Island Restoration, Caillou Lake Headlands Barrier Island Restoration, and North Breton Island Restoration (https://www. gulfspillrestoration.noaa.gov/louisiana-outer-coast-restoration, NOAA 2018). Shell Island and Chenier Ronquille are critical pieces of barrier shoreline within the Barataria Basin in Plaquemines Parish, Louisiana. These large-scale restoration projects were completed in the years following the Deepwater Horizon incident, creating new habitat and reinforcing Louisiana’s Gulf of Mexico shoreline. The Louisiana Coastal Protection and Restoration Authority (CPRA) finished construction of the Shell Island NRDA Restoration Project in 2017, which restored two barrier islands in Plaquemines Parish utilizing sand hydraulically dredged from the Mississippi River and pumped via pipeline over 20 miles over levees and through towns, marinas, and marshes to the coastline. The National Marine Fisheries Service (NMFS) also completed the Plaquemines Parish barrier island restoration at Chenier Ronquille in 2017 utilizing nearshore Gulf of Mexico sediment, restoring wetland, coastal, and nearshore habitat in the Barataria Basin. A design and construction overview is provided herein.

Coastal monitoring and data management for restoration in Louisiana

The Coastal Protection and Restoration Authority (CPRA) of Louisiana was created after the devastating hurricanes of 2005 (Katrina and Rita) and is responsible for planning and implementing projects that will either reduce storm-induced losses (protection) or restore coastal ecosystems that have been lost or are in danger of being lost (restoration). The first task of the CPRA board was to develop Louisiana’s first Coastal Master Plan (CPRA 2007), which formally integrates and guides the protection and restoration of Louisiana’s coast. The System-Wide Assessment and Monitoring Program (SWAMP) was subsequently developed as a long-term monitoring program to ensure that a comprehensive network of coastal data collection activities is in place to support the planning, development, implementation, and adaptive management of the protection and restoration program and projects within coastal Louisiana. SWAMP includes both natural-system and human-system components and also incorporates the previously-developed Coastwide Reference Monitoring System (CRMS), the Barrier Island Comprehensive Monitoring (BICM) program, and fisheries data collected by the Louisiana Department of Wildlife and Fisheries (LDWF) in addition to other aspects of system dynamics, including offshore and inland water-body boundary conditions, water quality, risk status, and protection performance, which have historically not been the subject of CPRA-coordinated monitoring. This program further facilitates the integration of project-specific data needs into a larger, system-level design framework. Monitoring and operation of restoration and protection projects will be nested within a larger hydrologic basin-wide and coast-wide SWAMP framework and will allow informed decisions to be made with an understanding of system conditions and dynamics at multiple scales. This paper also provides an update on the implementation of various components of SWAMP in Coastal Louisiana, which began as a Barataria Basin pilot implementation program in 2015. During 2017, the second phase of SWAMP was initiated in the areas east of the Mississippi River. In 2019, development of SWAMP design was completed for the remaining basins in coastal Louisiana west of Bayou Lafourche (Figure 1). Data collection is important to inform decisions, however if the data are not properly managed or are not discoverable, they are of limited use. CPRA is committed to ensuring that information is organized and publicly available to help all coastal stakeholders make informed, science-based decisions. As a part of this effort, CPRA has re-engineered its data management system to include spatial viewers, tabular download web pages, and a library/document retrieval system along with a suite of public-facing web services providing programmatic access. This system is collectively called the Coastal Information Management System (CIMS). CPRA and U.S. Geological Survey (USGS) are also developing a proposal to create an interface for CIMS data to be exported to a neutral template that could then be ingested into NOAA’s Data Integration Visualization, Exploration and Reporting (DIVER) repository, and vice versa. DIVER is the repository that the Natural Resource Damage Assessment (NRDA) program is using to manage NRDA-funded project data throughout the Gulf of Mexico. Linking CIMS and DIVER will make it easier to aggregate data across Gulf states and look at larger, ecosystem-level changes.

Effects of Mississippi River water on phytoplankton growth and composition in the upper Barataria estuary, Louisiana

Diversion of river waters to adjacent estuaries may occur during wetland restoration, navigation channel development, or storms. We proposed that diversions of nitrogen- and phosphorus-enriched waters from the river to estuarine waters would result in increased phytoplankton biomass and shifts to noxious or harmful algal blooms. We tested this hypothesis by conducting four seasonal microcosm experiments in which Mississippi River water was mixed at different volume ratios with ambient estuarine waters of three lakes in the upper Barataria Basin, Louisiana, USA. These lakes included two brackish lakes that were in the path of diverted Mississippi River water, and a freshwater lake that was not. The results from the 3- to 8-day experiments yielded a predictable increase in phytoplankton biomass related to nutrient additions from Mississippi River water. The subsequent decreases in the dissolved nitrate + nitrite, soluble reactive phosphorus, and silicate concentrations explained 76 to 86% of the increase in chlorophyll a concentrations in the microcosms. Our experiments showed that cyanobacteria can successfully compete with diatoms for N and P resources even under non-limiting Si conditions and that toxic cyanobacteria densities can increase to bloom levels with increased Mississippi River water inputs to ambient waters in the microcosms. Diversions of Mississippi River into adjacent estuarine waters should be considered in relation to expected and, possibly, unexpected changes in phytoplankton communities to the receiving waters and coastal ecosystems.

Wave dynamics near Barataria Bay tidal inlets during spring–summer time

The wave characteristics and wave–current interaction in the six tidal inlets connecting the Barataria Basin and the northern Gulf of Mexico are investigated during spring–summer time period when both cold front passage and persistent southeast wind events exist. A fully-coupled unstructured-grid, three-dimensional, FVCOM-SWAVE model is employed and validated against observational data during April–June 2010. Model simulation results indicate that waves in the shelf side of the inlets are mainly wind seas and swells from the Gulf of Mexico that are modified by ocean currents in the Louisiana Bight. These currents include Mississippi River plume, buoyancy- and wind-driven alongshore current, as well as the tidal jet in the Barataria Pass. The bay side of the inlets, similar to the interior of the Barataria Basin, is dominated by locally generated waves. In the middle of the inlets, both wind seas and swells are presented at times, though different inlets behave differently in terms of contribution from each component. The contribution of local wind seas enhances during cold front passage. Contrastingly, the influence of swells from continental shelf is more pronounced during persistent southeast wind event. FVCOM-SWAVE predicts a decrease in significant wave height inside the Louisiana Bight due to current-induced refraction and wave stretching effect caused by clockwise gyre from Mississippi plume. The modulation of significant wave height at Barataria Pass due to partial wave blocking for the opposing current, and wave stretching for the following current can be up to 20%. The effect of depth-induced breaking and bottom friction overshadows the one from wave–current interaction at other shallower inlets.

Lignin chemistry of wetland soil profiles in two contrasting basins of the Louisiana Gulf coast

Recent studies indicate that loss of soil organic matter (SOM) from coastal wetlands can contribute to the hypoxia in the northern Gulf of Mexico along the Louisiana coast. In this study, coastal marsh soil profiles of two contrasting basins were investigated for lignin composition in order to assess organic matter source and degradation status under these different wetland formations. The Atchafalaya Basin is undergoing land building whereas the Barataria Basin is experiencing land loss. Lignin monomers were extracted using alkaline CuO oxidation followed by gas chromatography–mass spectrometry characterization. Marsh soil profiles from the Barataria Basin showed strong lignin storage with two-fold higher lignin contents (sum of vanillyl, syringyl, and cinnamyl phenols, Λ8) than those in the Atchafalaya Basin. Source SOM inputs in the Barataria Basin were non-woody angiosperms, whereas in the Atchafalaya Basin inputs were non-woody angiosperms and some gymnosperm inputs. Principal component analysis (PCA) showed that different soil environmental factors dominated the status of soil organic matter degradation. Soil pH was negatively related to the lignin degradation in the Atchafalaya Basin, whereas high total N contents inhibited lignin degradation in the Barataria Basin. Increasing electrical conductivity inhibited organic matter degradation in the low salinity wetlands of the Atchafalaya Basin, but positively influenced lignin decomposition in the higher salinity marsh soil profiles of Barataria Basin. Despite SOM in the Barataria Basin being more degraded than in the Atchafalaya, the nearly 10-fold greater amount of organic carbon (C) in the Barataria, coupled with net land loss, indicates that it is greater source of oxygen-consuming organic C, thus contributes more to the hypoxia in the Gulf.

Marsh edge erosion and associated carbon dynamics in coastal Louisiana: A proxy for future wetland-dominated coastlines world-wide

Coastal wetland loss through marsh edge erosion is a serious problem in Louisiana. The majority of studies on coastal land loss use aerial and satellite photographic analysis while field and site-specific measurements are limited. The aim of this study was to spatially and temporally measure coastal marsh edge erosion and investigate factors responsible for differences in erosion including shoreline orientation, soil physio-chemical properties, and wind speed and duration. A total of 33 transects across six island sites in northern Barataria Basin, Louisiana were established. Transects on shorelines facing different compass directions were measured for erosion for up to 2 years. Soils were analyzed for physiochemical properties including bulk density, organic matter, total carbon, nitrogen, and phosphorus. Bathymetric surveys were conducted to determine the extent of the erosive bay bottom profile. In addition, 14C dating of the basal organic matter (1.5–1.6 m) was conducted. Erosion rates ranged from 49.27 to 324.85 cm y-1 with a mean value of 141.69 ± 22.45 cm y−1. As expected, erosion rates were significantly different (p < 0.001) between protected and unprotected sites. The erosion rate was not correlated with wind speed (r = -0.07), weakly correlated with compass direction of shoreline (r = 0.25) and water level (r = 0.25) but strongly correlated with duration of wind (r = 0.60). Erosion rate was negatively correlated (r = -0.45) with bulk density and positively correlated with organic matter content (r = 0.42) of the top 40 cm of the soil. Over time, the marsh is eroded down to a depth of 1.5 m, which correlates to annual loss of 1.82 ± 0.29 m3 volume of marsh per meter shoreline length including a loss of organic matter (141.5 ± 22.55 kg m−1) and carbon (63.32 ± 10.09 kg m−1) previously preserved for up to 850 years. As a consequence, annual CO2 emissions for Barataria Basin were estimated to be 1.56 ± 0.26 million tCO2e y−1. Results can inform coastal managers as to the most vulnerable marshes to target restoration efforts. Due to high relative sea level rise in coastal Louisiana, these results can also be used to inform the world's stable coastlines on the relative vulnerability of their coastal marshes in the near future, due to projected eustatic sea level. Consequently, the eroding coastlines across the globe may be a significant source of CO2 emissions in near future, as millennial age stored soil carbon is released in a relatively short time, potentially overwhelming human efforts to slow rising atmospheric CO2 levels.

The denitrification potential of eroding wetlands in Barataria Bay, LA, USA: Implications for river reconnection

Expressions of eutrophication have led to increased stress on coastal ecosystems around the world. The nitrogen (N) removal potential of coastal wetland ecosystems is important due to increased loading of N to the coast. In Louisiana, there is rapid coastal wetland loss due primarily to the presence of river levees, which have isolated the coastal basins, and a high relative sea level rise. Ecosystem managers are planning to construct the Mid-Barataria sediment diversion which will reconnect the Mississippi River with Barataria Basin to build new wetlands and nourish existing marsh. The sediment diversion will deliver large amounts of nitrate into the surface waters of Barataria Bay. This research sought to quantify the nitrate removal potential of three bay zones; vegetated marsh, submerged peat fringe, and bay-bottom muddy estuarine sediment in intact soil cores incubated with a 2 mg L−1 N-NO3 water column. We noted: i) The areal nitrate reduction rates for the marsh, fringe, and estuary zones were 29.29 ± 3.28, 18.83 ± 1.31, and 10.83 ± 0.62 mg N m−2 day−1, respectively; ii) the majority (~93%) of NO3 was converted to N2O, indicating denitrification was the major NO3 reduction pathway; iii) the submerged, eroded marsh soils (peat fringe zone) will play a large role in nitrate reduction due to increased contact time with the surface water. These findings can inform the predictive numerical models produced and utilized by ecosystem managers to better quantitatively understand how the coastal basin will respond to nutrient loading from river reconnection. In a broader context, the current relative sea level rise in coastal Louisiana is within the range of eustatic sea level rise that most stable coastlines will experience within the next 65–85 years. Therefore, these findings can serve as an example of potential future impacts to coastal wetland systems, globally, within the next century.

Recent subsidence rates for Barataria Basin, Louisiana

Subsidence in south Louisiana is a fundamental process and major source of uncertainty influencing restoration planning and design and wetland habitat resilience. The primary goal of this study was to conduct an analysis of recent subsidence rates within the Barataria Basin. High-resolution geodetic GPS elevation measurements at 19 benchmarks were used to determine recent subsidence rates for the Barataria Basin. Net elevation changes at all stations equaled or exceeded predicted measurement uncertainties based on session duration. Water elevation change from two gauges in the southern part of the basin supplemented survey data, resulting in a range of subsidence velocities at 21 locations from about 2 to 7 mm/year. These data record short-term subsidence trends (6- to 16-year time series) that are expected to be representative of conditions at proposed restoration sites over the next 20 to 50 years. Foundation/rod depths for benchmarks ranged from near surface to about 30-m deep. None of these foundations/rods were sleeved or anchored and thus were not isolated from surrounding consolidating sediment and associated downdrag forces. Therefore, subsidence rates at these sites were considered representative for the entire sediment column. Subsidence rate comparisons for nearby deep and shallow rod benchmarks support this conclusion. Spatial variability in subsidence indicates a compelling relationship between subsidence rates and the age, composition, and thickness of Holocene deltaic deposits. The Coastal Protection and Restoration Authority of Louisiana intends to use this same approach to continue refining subsidence rates throughout coastal Louisiana to support coastal restoration planning and design.

Multi-decadal trends and influences on dissolved organic carbon distribution in the Barataria Basin, Louisiana from in-situ and Landsat/MODIS observations

Barataria Basin, a deltaic marsh-estuary system in the northern Gulf of Mexico (nGOM), is an important source of dissolved organic matter (DOM) to the coastal ecosystem. To assess DOM dynamics, monthly measurements of dissolved organic carbon (DOC) concentrations and colored DOM (CDOM; an optical proxy for DOC) absorption were obtained over a three-year period (2008–2011) along a transect encompassing the upper, middle and lower regions of the Barataria Basin estuary. While CDOM absorption coefficient at 355 nm (ag355) generally decreased and spectral slope at 275–295 nm (S275–295) increased along the transect from the upper to lower basin, deviations were observed associated with hydrologic and meteorological influences. An application of wavelet analysis to the time-series of ag355 and various freshwater sources revealed a spatiotemporal resonance of ag355 with freshwater input from the Mississippi River (MR), the controlled freshwater discharge from the Davis Pond freshwater diversion, and rainfall in the lower, middle and upper basins, respectively. Field measurements and Landsat/MODIS data spanning across different seasons between 2008 and 2011 were used to develop optimized ag355 empirical algorithms for the high river flow, cold front, and normal conditions. Power law models relating a band ratio (green/red) of a satellite sensor to ag355 showed good performance for the MODIS-Aqua (R2~0.81–0.83, N = 581) and Landsat-5 TM (R2~0.72–0.79, N = 304) imagery. ag355-DOC relationships (R2~0.77–0.84, N = 306) applied to historical Landsat-5 TM (1985–2011) and MODIS-Aqua imagery (2002−2012) showed strong environmental influences on multi-decadal CDOM and DOC spatiotemporal trends. Satellite-derived DOC agreed reasonably well with in-situ measured DOC (averaged R2 = 0.71; RMSE = 2.13). While the time-series DOC showed seasonality and decreasing gradients from the upper to lower basin, an overall increase in DOC was observed in the upper and middle basins from 1985 to 2012. However, in the lower basin, DOC increased from 1985 to 2006 but decreased from 2007 to 2012, likely due to the impact of two major hurricanes in 2005. Furthermore, relationships between satellite-derived DOC and land cover variations (1985–2011) along the wetland-estuary interfaces derived from Landsat-5 TM supervised classification showed an increase in DOC with corresponding increase in developed area in the upper basin, while in the lower basin, DOC increased by 41% (R2 = 0.54) between 1985 and 2006 corresponding to a 17% decrease in salt marsh area, suggesting strong land use/land loss impact on the long-term DOC trends in Barataria Basin.

Spatial variations in Chlorophyll a, C, N, and P in a Louisiana estuary from 1994 to 2016

Intense sampling of an estuary can reveal relative spatial changes that are significant irrespective of whether or not the estuary is eutrophic, micro- or meso-tidal, disturbed, or restored. This ‘waterscape’ perspective is analogous to a landscape perspective. We collected monthly water samples in the Barataria Basin watershed from 1994 to 2016 at 37 stations along a 129 km transect from 1 km offshore to a freshwater stream. The average Chlorophyll a (Chl) concentration from 267 trips was supported from both nitrogen-fixing cyanobacteria in a freshwater lake and partially from nutrients in seaward sources. Estuarine salinity was correlated with the discharge of the nearby Mississippi River. The main form of N was as organic nitrogen, not inorganic forms that recycle quickly, making changes in inorganic nitrogen concentration an unreliable indicator of net denitrification or uptake. The total nitrogen (TN) and total phosphorus (TP) concentrations declined with dilution towards the coast, but not because of denitrification. The phytoplankton standing biomass reflected the TN:TP ratio in the water column and there was a significant rise in the variability of Chl concentration at 2–6 psu, which was otherwise unremarkably constant. These waterscape patterns and cautionary interpretations may be common to other estuaries.

Salinity and Marine Mammal Dynamics in Barataria Basin: Historic Patterns and Modeled Diversion Scenarios

Understanding spatiotemporal patterns of salinity in Barataria Basin in coastal Louisiana is important to better understand and manage operations of existing and proposed freshwater and sediment diversions from the Mississippi River into the estuary. In this study, a comprehensive salinity dataset was compiled which covered the entire basin and included data from 1990 through 2015. The data were aggregated into daily mean salinity timeseries across Barataria Basin at a variety of spatial scales and used to analyze historic patterns. Simulations were conducted with two hydrodynamic models, the Integrated Compartment Model (ICM) and Delft3D. The Delft3D model output was overlaid with observed geo-tagged locations of bottlenose dolphins that were sampled from the southwest quadrant of the basin. The ICM simulations were used to assess the impact of existing freshwater and proposed sediment diversion projects which reintroduce riverine water into the estuary. The salinity in the uppermost portions of the basin is sensitive primarily to the existing freshwater diversion, whereas additional flows from a proposed sediment diversion result in additional freshening. The lowermost region of the basin is most sensitive to the proposed sediment diversion; however, the magnitude varies by diverted flow volumes and assumed sea levels in the Gulf of Mexico.

The tensile root strength of five emergent coastal macrophytes

The root biomass of emergent macrophytes in coastal wetlands is essential for anchorage and erosion protection. The tensile root strength of these plants is an important component in determining the strength of coastal wetland soils. We made 1449 tensile strength measurements of roots <1.5 mm in diameter for five species of emergent wetland macrophytes (Spartina alterniflora, S.patens, Panicum hemitomon, Schoenoplectus americanus, and Sagittaria lancifolia) collected from six sites in three coastal estuaries. An analysis of variance revealed that the tensile root strength of dead and live roots for all species decreased with depth and that dead roots were stronger than live roots of the same diameter (p < 0.05). There was low variation in the mean tensile root strength among all sites. The S. alterniflora dead roots from the Barataria Basin site, however, were stronger than those from the Lake Pontchartrain site and the S. patens live and dead roots collected from Breton Sound were stronger than those from a nearby site in the same watershed. Wetland root samples exposed to partially-treated sewage effluent were considerably smaller than roots collected from the nearby reference wetland. Further investigation is warranted to ascertain the nature of the factors that causing these variations in tensile root strength with depth, between live and dead roots and with nutrient exposure

Airborne electromagnetic profiling in the Gulf of Mexico

First, I will give an overview of the research on Airborne Electromagnetic Profiling (AEM) by the University of New Orleans (UNO) group that included George Ioup. The standard techniques of error correction, calibration, modeling, inverse methods, interpolation, and smoothing were used to convert raw profiler data into meaningful data and useful products. As a part of a NASA EPSCoR project, the group applied layer models to AEM data to measure shallow water bathymetry and water column stratification in the Gulf of Mexico and coastal near surface geomorphology in the Barataria basin of Louisiana. In the second part of the talk, I will sketch the history of the UNO Engineering and Applied Science doctoral program and George Ioup's large role in it.

Biomarkers of Aryl-hydrocarbon Receptor Activity in Gulf Killifish (Fundulus grandis) From Northern Gulf of Mexico Marshes Following the Deepwater Horizon Oil Spill.

Following the Deepwater Horizon oil spill, shorelines throughout the Barataria Basin of the northern Gulf of Mexico in Louisiana were heavily oiled for months with Macondo-252 oil, potentially impacting estuarine species. The Gulf killifish (Fundulus grandis) has been identified as a sentinel species for the study of site-specific effects of crude oil contamination on biological function. In November and December 2010, 4-5months after the Macondo well was plugged and new oil was no longer spilling into the Gulf waters, Gulf killifish were collected across the Barataria Basin from 14 sites with varying degrees of oiling. Fish collected from oiled sites exhibited biological indications of exposure to oil, including increase in cytochrome P4501A (CYP1A) mRNA transcript and protein abundances in liver tissues. Immunohistochemistry revealed increases in gill, head kidney, and intestinal CYP1A protein at heavily oiled sites. Intestinal CYP1A protein was a sensitive indicator of exposure, indicating that intestinal tissue plays a key role in biotransformation of AHR ligands and that ingestion is a probable route of exposure, warranting additional consideration in future studies.

Water quality of a coastal Louisiana swamp and how dredging is undermining restoration efforts

The Bayou Boeuf Basin (BBB), a sub-basin of the Barataria Basin estuary in coastal Louisiana, consists of forested and floating wetlands receiving drainage from surrounding agricultural fields and urban watersheds. We characterized surface water quality in the BBB, and determined through hydrologic modeling if a series of levee breaks along major drainage channels would significantly improve water quality by allowing flow into surrounding wetlands. Surface water monitoring found surrounding sugarcane farm fields to be major sources of nutrient and sediment loading. Hydrological modeling indicated that levee breaks would increase N reduction from the current 21.4% to only 29.2%, which is much lower than the anticipated 90–100% removal rate. This was due to several factors, one them being dredging of main drainage channels to such a degree that water levels do not rise much above the surrounding wetland elevation even during severe storms, so only a very small fraction of the stormwater carried in the channel is exposed to wetlands. These unexpected results provide insight into an undoubtedly pervasive problem in human dominated wetland systems; that of decreased flooding during storm events due to channel deepening by dredging activities. Additional water quality management practices should be implemented at the farm field level, prior to water entering major drainage canals.

Freshwater diversions as an ecosystem management tool for maintaining soil organic matter accretion in coastal marshes

Abstract Marsh soil accretion processes were examined at 12 locations in fresh and brackish marshes in Louisiana's northern Barataria Basin estuary. Soil accretion rate determined from 137 Cs ranged from 0.59 to 1.03 cm yr − 1 . Soil structure and accretion were controlled primarily by organic matter accumulation rather than mineral sediment deposition with water and entrapped gases occupying the majority of the soil volume ranging from 92 to 95%. Organic matter accumulation ranged from 328 to 580 g m − 2 yr − 1 while mineral accumulation ranged from 78 to 380 g m − 2 yr − 1 Such organic-based fresh and brackish marsh soil are more fragile than mineral based marsh soils and are subject to impact by salt water intrusion and hurricane storm surge forces. The Davis Pond diversion is a conduit between the Mississippi River and the coastal marshes of Barataria basin currently reintroducing river water into the basin leading to lower basin salinities This hydrologic management measure should benefit and extend the stability of the studied marsh sites encouraging continued vegetation growth and soil organic matter accumulation. Accrual of organic matter is necessary to prevent drowning of the marsh which is subject to both the global eustatic sea level rise (1–2 mm yr − 1 ) and significant local subsidence (~ 10 mm yr − 1 ). This high rate of relative sea level rise can lead to open water/ponding and subsequent erosion of the surrounding marsh due to flooding and salinity stress.

Molecular Composition of Humic Acids from Coastal Wetland Soils along a Salinity Gradient

Humic acids (HAs) play an important role in regulating the biogeochemistry of soils and sediments. The chemical structural composition of humic substances in wetland soils especially at coastal zone, which is subjected to the influence of seawater intrusion, is not yet fully understood. In this study, HAs from soils of three wetland ecosystems along a salinity gradient namely, a forest swamp (FS), freshwater marsh (FM), and saline marsh (SM), from the Barataria basin of the Louisiana coast were isolated and characterized using elemental analysis, 13C solid state nuclear magnetic resonance (NMR), and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) with or without tetramethylammonium hydroxide (TMAH) treatment. Humic acids from the FS soil, the most inland of the three, showed the most aliphatic nature whereas HAs of the FM soil had the highest percentage of aromatics. There was a general increase in the crystalline domain of alkyl C in these wetland soil HAs along the salinity gradient. The Py-GC/MS TMAH thermochemolysis clearly showed a shift of lignin residues from the dominance of guaiacyl (G-type) and syringyl (S-type) structural units in FS HAs to p-hydroxyphenyl (H-type) structural unit in HAs of both marsh soils. In addition, there was a smaller Syringyl/Guaiacyl (S/G) ratio in the HAs of SM soil than FM soil, and an increasing contribution of sulfur compounds into their HA structural component as moving toward the coast, suggesting the formation of increasingly more recalcitrant nature of HAs along the salinity gradient in these wetlands. The 13C NMR observation was, in general, consistent with the Py-GC/MS characterization. Overall, the result reveals a clear effect of salinity and vegetation on the molecular composition of HAs.